Magnetohydrodynamics modelling of a permanent magnets activated MRF clutch–brake

Abstract

Chattering due to vibrations on the machine tool shaft and control of the transmitted torque are both a concern in precision machining. Hence, a magnetorheological fluid clutch–brake, also acting as a rotary damper could be a promising solution. Permanent magnets are used to mechanically activate the clutch thus offering simplicity and reliability in operation. The viscosity of the magnetorheological fluid changes with the action of the magnetic field thus allowing to tune the transmitted torque. Moreover, the fluid adds damping in the system. In this paper, a computational magnetohydrodynamics model has been realized in order to numerically investigate and visualize the torque transmission under different rotational velocities when submitted to magnetic flux. The model was validated with experimental data from the literature. Results showed that because the permanent magnets have a limited flux intensity, the torque transmission is only efficient at lower rotational velocities.